This gets called when a button is clicked
#Override
public void onFavoriteIconClicked() {
viewModel.isFavoriteExist(test.getId()).observe(getViewLifecycleOwner(), new Observer<Boolean>() {
#Override
public void onChanged(Boolean aBoolean) {
viewModel.isFavoriteExist(test.getId()).removeObserver(this);
if (aBoolean) {
binding.addToFavorite.setImageResource(R.drawable.non_fav);
viewModel.delete(test);
} else if (getActivity() != null) {
Test test2 = new Test(test.getId(), test.getName());
viewModel.insert(test2);
binding.addToFavorite.setImageResource(R.drawable.fav);
}
}
});
}
If the test object exists in the Favorite database, I have to delete it. After deleting, it calls this again (since it observed a chane) and inserts it again.
It keeps looping infinitely. Is there a better way to implement this or stop this?
It seems like some business logic has entered your view (Activity) class.
Since LiveData & Room are meant to be used when receiving updates about Database changes is needed, and your use of the DB is not requiring constant updates, I would suggest going with a more direct approach.
First, Remove the use of LiveData from your Database. Use simple return values.
Your view (Activity/Fragment) can then tell the view model that a button was clicked.
#Override
public void onFavoriteIconClicked() {
viewModel.onFavoriteClicked()
}
The view will observe the view model in order to receive the correct icon to show.
Something like:
viewModel.favoriteIcon.observe(getViewLifecycleOwner(), new Observer<Integer>() {
#Override
public void onChanged(Integer iconResId) {
binding.addToFavorite.setImageResource(iconResId)
}
}
Now the viewModel can handle the logic (or better add a Repository layer - See Here)
Upon click, Check if entry exist in DB.
If exists: remove it from DB and set favoriteIcon value:
favoriteIcon.setValue(R.drawable.non_fav)
If doesn't exist: Add it to DB and set favoriteIcon value.
favoriteIcon.setValue(R.drawable.fav)
For a good tutorial about using Room & LiveData - as well as doing so using the View/ViewModel/Repository pattern, check this link
I want to know what is the best approach to display some sort of message in the view from the ViewModel. My ViewModel is making a POST call and "onResult" I want to pop up a message to the user containing a certain message.
This is my ViewModel:
public class RegisterViewModel extends ViewModel implements Observable {
.
.
.
public void registerUser(PostUserRegDao postUserRegDao) {
repository.executeRegistration(postUserRegDao).enqueue(new Callback<RegistratedUserDTO>() {
#Override
public void onResponse(Call<RegistratedUserDTO> call, Response<RegistratedUserDTO> response) {
RegistratedUserDTO registratedUserDTO = response.body();
/// here I want to set the message and send it to the Activity
if (registratedUserDTO.getRegisterUserResultDTO().getError() != null) {
}
}
});
}
And my Activity:
public class RegisterActivity extends BaseActivity {
#Override
protected int layoutRes() {
return R.layout.activity_register;
}
#Override
protected void onCreate(Bundle savedInstanceState) {
AndroidInjection.inject(this);
super.onCreate(savedInstanceState);
ActivityRegisterBinding binding = DataBindingUtil.setContentView(this, layoutRes());
binding.setViewModel(mRegisterViewModel);
}
What would the best approach be in this case?
We can use a SingleLiveEvent class as a solution. But it is a LiveData that will only send an update once. In my personal experience, using an Event Wrapper class with MutableLiveData is the best solution.
Here is a simple code sample.
Step 1 :
Create an Event class (this is a boilerplate code you can reuse for any android project).
open class Event<out T>(private val content: T) {
var hasBeenHandled = false
private set // Allow external read but not write
/**
* Returns the content and prevents its use again.
*/
fun getContentIfNotHandled(): T? {
return if (hasBeenHandled) {
null
} else {
hasBeenHandled = true
content
}
}
/**
* Returns the content, even if it's already been handled.
*/
fun peekContent(): T = content
}
Step 2 :
At the top of your View Model class, define a MutableLiveData with wrapper (I used a String here, but you can use your required data type), and a corresponding live data for encapsulation.
private val statusMessage = MutableLiveData<Event<String>>()
val message : LiveData<Event<String>>
get() = statusMessage
Step 3 :
You can update the status message within the functions of the ViewModel like this:
statusMessage.value = Event("User Updated Successfully")
Step 4 :
Write code to observe the live data from the View (activity or fragment)
yourViewModel.message.observe(this, Observer {
it.getContentIfNotHandled()?.let {
Toast.makeText(this, it, Toast.LENGTH_LONG).show()
}
})
Display Toast/snackbar message in view (Activity/Fragment) from viewmodel using LiveData.
Step:
Add LiveData into your viewmodel
View just observe LiveData and update view related task
For example:
In Viewmodel:
var status = MutableLiveData<Boolean?>()
//In your network successfull response
status.value = true
In your Activity or fragment:
yourViewModelObject.status.observe(this, Observer { status ->
status?.let {
//Reset status value at first to prevent multitriggering
//and to be available to trigger action again
yourViewModelObject.status.value = null
//Display Toast or snackbar
}
})
I have an List called messages property in my Activity.In the synchronization(),I called getDateMessage(upadated_at) function.In this function value of messages has changed but when program go to synchronization messages list is empty.
private List<message_model> messages = new ArrayList<>();
private void synchronization() {
getDateMessage(upadated_at);
Log.e("MSDF",messages.toString()+" list tostring");
}
private void getDateMessage(String date) {
MessengerActivity.APIInterface apiInterface = app_net.getRetrofitInstance().create(MessengerActivity.APIInterface.class);
retrofit2.Call<List<message_model>> call = apiInterface.getMessageDate(Ptoken, date);
call.enqueue(new Callback<List<message_model>>() {
#Override
public void onResponse(Call<List<message_model>> call, Response<List<message_model>> response) {
if(response.isSuccessful()) {
messages.addAll(response.body());
Log.e("MSDF",response.body().toString()+" responsebody in call");
Log.e("MSDF",messages.toString()+" message in call");
Log.e("MESSAGE", "getDateMessage successful");
}
}
#Override
public void onFailure(Call<List<message_model>> call, Throwable t) {
Log.e("MESSAGE", "getDateMessage" + t.toString());
}
});
}
And This is my logcat.
09-30 14:34:53.714 10763-10763/idea.mahdi.bime E/MSDF: [] list tostring
09-30 14:34:54.104 10763-10763/idea.mahdi.bime E/MSDF: [message_model{id=33, thread_id=2, user_id=15, body='چطوری', created_at='2018-09-29 10:28:26', updated_at='2018-09-29 10:28:26', deleted_at='null'}, message_model{id=30, thread_id=2, user_id=15, body='سلام', created_at='2018-09-29 09:30:40', updated_at='2018-09-29 09:30:40', deleted_at='null'}, message_model{id=7, thread_id=2, user_id=15, body='hi', created_at='2018-09-24 09:55:46', updated_at='2018-09-24 09:55:46', deleted_at='null'}] responsebody in api
09-30 14:34:54.104 10763-10763/idea.mahdi.bime E/MSDF: [message_model{id=33, thread_id=2, user_id=15, body='چطوری', created_at='2018-09-29 10:28:26', updated_at='2018-09-29 10:28:26', deleted_at='null'}, message_model{id=30, thread_id=2, user_id=15, body='سلام', created_at='2018-09-29 09:30:40', updated_at='2018-09-29 09:30:40', deleted_at='null'}, message_model{id=7, thread_id=2, user_id=15, body='hi', created_at='2018-09-24 09:55:46', updated_at='2018-09-24 09:55:46', deleted_at='null'}] message in api
09-30 14:34:54.104 10763-10763/idea.mahdi.bime
E/MESSAGE: getDateMessage successful
The problem is that when you call getDataMessage() it performs an asynchronous call (the retrofit enqueue() method). The server will be called to get the messages in a backgroud thread, while the android application will keep in the main thread.
Therefore, Log.e("MSDF",messages.toString()+" list tostring"); is called before the retrofit call is made, hence, there is no current data available yet. You should make sure that you are doing something with the data after it is completed loaded.
private List<message_model> messages = new ArrayList<>();
private void synchronization() {
getDateMessage(upadated_at);
// Anything you put here will be called before the data (messages) is loaded.
// Do not work with your messages here, they'll be null.
}
private void getDateMessage(String date) {
MessengerActivity.APIInterface apiInterface = app_net.getRetrofitInstance().create(MessengerActivity.APIInterface.class);
retrofit2.Call<List<message_model>> call = apiInterface.getMessageDate(Ptoken, date);
call.enqueue(new Callback<List<message_model>>() {
#Override
public void onResponse(Call<List<message_model>> call, Response<List<message_model>> response) {
if(response.isSuccessful()) {
messages.addAll(response.body());
Log.e("MSDF",response.body().toString()+" responsebody in call");
Log.e("MSDF",messages.toString()+" message in call");
Log.e("MESSAGE", "getDateMessage successful");
// Anything you want to do with the messages should be placed here. When you are sure the data is completed.
Log.e("MSDF",messages.toString()+" list tostring");
}
}
#Override
public void onFailure(Call<List<message_model>> call, Throwable t) {
Log.e("MESSAGE", "getDateMessage" + t.toString());
}
});
}
It's worth checking if (response.body() != null) before doing something with it to avoid NPE.
EDIT
As it was asked in the comments. A good solution (Google recommends it) is to fetch the data using a view model as described in this android dev guide article.
ViewModel approach is good because:
The data persist during configuration changes (for example, if you rotate your device, your list of messages will be still in your app).
It does not cause memory leaks.
You separate view data ownership from UI controller logic.
You can see the other advantages in the article.
1 - Add the view model dependecies in your build.gradle(Module:app) file
dependencies {
def lifecycle_version = "1.1.1"
// ViewModel and LiveData
implementation "android.arch.lifecycle:extensions:$lifecycle_version"
}
See here the latest version.
2 - Create a ViewModel class
MessageViewModel.java
public class MessagesViewModel extends ViewModel {
private MutableLiveData<List<message_model>> messagesList;
public LiveData<List<message_model>> getMessages() {
if (messagesList == null) {
messagesList = new MutableLiveData<List<message_model>>();
loadMessages();
}
return messagesList;
}
private void loadMessages() {
MessengerActivity.APIInterface apiInterface = app_net.getRetrofitInstance().create(MessengerActivity.APIInterface.class);
retrofit2.Call<List<message_model>> call = apiInterface.getMessageDate(Ptoken, date);
call.enqueue(new Callback<List<message_model>>() {
#Override
public void onResponse(Call<List<message_model>> call, Response<List<message_model>> response) {
if(response.isSuccessful()) {
if (response.body() != null) {
messagesList.setValue(response.body());
}
}
}
#Override
public void onFailure(Call<List<message_model>> call, Throwable t) {
// Handle failure
}
});
}
}
3 - Get the messages in your activity
public class MainActivity extends AppCompatActivity {
public void onCreate(Bundle savedInstanceState) {
// Create a ViewModel the first time the system calls an activity's onCreate() method.
// Re-created activities receive the same MyViewModel instance created by the first activity.
MessagesViewModel model = ViewModelProviders.of(this).get(MessagesViewModel.class);
model.getMessages().observe(this, messagesList -> {
// Do whatever you want with the list of messages.
});
}
}
Look how clean your activity is now.
Then you can implement a SwipeRefreshLayout if you want to allow your users to refresh the data.
If it is not enough, you can check this ReposViewModel
Finally, if calling retrofit is the main core of your app that is going to be released to the public, you should introduce MVVM approach using Dagger 2 and RxJava, as described in this article. (This is advanced)
I'm trying to implement a Google Fit Listener when data is updated into Google Fit services.
In this link of Google Fit documentation there is a simple example, however, it is not 100% clear. For that reason, I have two problems:
I don't know how to implement mResultCallback variable (there aren't any examples in this documentation).
When I define a simple ResultCallback (it seems to work but I'm not sure) and I launch the application, it gives me a result error code: java.lang.SecurityException: Signature check failed
The code within the HistortyApi lists one of android.permission.ACCESS_FINE_LOCATION or android.permission.BODY_SENSORS as being required.
Adding those permissions to my code hasn't resolved the same problem though.
Confirmed bug in Google Fit services. See discussion in https://plus.google.com/110141422948118561903/posts/Lqri4LVR7cD
mResultCallback is a ResultCallback<Status> so you need to implement a class of that type. Documentation is here, but there's only one method you need to implement:
public abstract void onResult (Status result)
The standard way is to do this using an anonymous class either when you declare mResultCallback or when you're using it as a parameter. Below is an example from Google's BasicRecordingAPI example:
Fitness.RecordingApi.subscribe(mClient, DataType.TYPE_ACTIVITY_SAMPLE)
.setResultCallback(new ResultCallback<Status>() {
#Override
public void onResult(Status status) {
if (status.isSuccess()) {
if (status.getStatusCode()
== FitnessStatusCodes.SUCCESS_ALREADY_SUBSCRIBED) {
Log.i(TAG, "Existing subscription for activity detected.");
} else {
Log.i(TAG, "Successfully subscribed!");
}
} else {
Log.i(TAG, "There was a problem subscribing.");
}
}
});
If you want to use a member variable you can simply make an assignment instead:
ResultCallback<Status> mResultCallback = new ResultCallback<Status>() {
#Override
public void onResult(Status status) {
...
}
});
Of course you can define a non-anonymous class, but if you did that for every callback you had you would end up creating a LOT of classes.
I have two swing ui forms and a module that they both look at.
Each ui is adding a listener to the change of an attribute
and update its own textfield when a change occurs.
basiccaly - they both should update the module and be update from it.
Is there a way simple to do it whithout a binding framework
Here is how I do it (but I keep getting attempt to mutate in notification ) -
On the update of my textField
myTextField.getDocument().addDocumentListener(new TFDocumentListener() {
protected void userChangedTF() {
Float value = myTextField.getValue();
if (value != null) {
myObj.setMyAttribute(value);
}
}
});
still in the ui - registering the change
myObj.addMyAttributeChangedListener(new ValueChangeListener<Float>() {
#Override public void valueChanged(Float value) {
if (!myTextField.isFocusOwner()) {
myTextField.setValueIn(value);
}
}
});
in the module - when setMyAttribute occurs - it calls this function
private void notifyIntervalChanged(float newValue) {
for (ValueChangeListener valueChangeListener : intervalChangedListenersList) {
valueChangeListener.valueChanged(newValue);
}
}
and I declared
public interface ValueChangeListener<T> {
void valueChanged(T Value)
}
If you need to change content of the same JTextComponent in the listener wrap the change (e.g. setText()) in the SwingUtilities.invokeLater()